Tube-bending machine

ABSTRACT

In a fully automatic cold tube-bending machine for production of serpentine coils from straight tubes of random lengths, a tube feeder not only measures the tube feed between successive bends, but also, after the last bend in any given tube, senses the tube end and measures the residual terminal length or the deficiency from the length to the next succeeding bend in a desired larger coil, and, by generating a corresponding control signal, initially feeds the next tube by the amount of the length deficiency, with allowance for any tubing length adjustment for the joint to be made between successive tubes; so that successively bent tubes may be appropriately joined without fitting or matching operations.

United States Patent [72] Inventors ErlchRitter [731 Assignees 1-1. Schwarze Sohne, Gebr. Schwarze,

Peter Wirtz K. G., CologneMerheim,

Germany [32] Priority Aug. 16, 1968 [33] Germany [31] P17 52 977.0

[54] TUBE-BENDING MACHINE 10 Claims, 4 Drawing Figs.

[52] US. Cl 72/7, 72/14, 72/24, 72/DIG. 22, 29/1573 R [51] Int. Cl B21b37/14, 83% 15/26 [50] Field oISearch 72/6, 7, 9,

[56] References Cited UNIT ED STATES PATENTS 2,979,103 4/1961 Bowman 72/24 2,814,327 11/1957 Charlton 72/24 2,565,940 8/195l Armstrong et al. 72/27 2,453,868 1 1/ 1948 Shaw, Jr. 72/7 Primary Examiner-Charles W. Lanham Assistant Examiner-Michael .l. Keenan Attorney-Ely, Golrick & Flynn ABSTRACT: In a fully automatic cold tube-bending machine for production of serpentine coils from straight tubes of random lengths, a tube feeder not only measures the tube feed between successive bends, but also, after the last bend in any given tube, senses the tube end and measures the residual terminal length or the deficiency from the length to the next succeeding bend in a desired larger coil, and, by generating a corresponding control signal, initially feeds the next tube by the amount of the length deficiency, with allowance for any tubing length adjustment for the joint to be made between successive tubes; so that successively bent tubes may be appropriately joined without fitting or matching operations.

PATENTED JUL 1 3 nan SHEET 1 BF 2 FIG.

TUBE-BENDING MACHINE The invention refers to a fully automatic tube cold bending machine for bending serpentine coils out of different straight tube lengths. This machine is equipped with a tube-feeding device for adjusting the lengths between the bends, and a tube-indexing device for adjusting the angle between two bends. With the aid of the invention, the tubes of random lengths can be used for producing a serpentine coil in a con tinuous bending process. The tube-feeding device feeds the leg of a serpentine bend as well as measures the stub tube length, remaining after the last bend of a given tube, and thereby the deficiency from the required coil leg length, in order to feed this length deficiency from the next tube in the subsequent feeding operation so that the necessary total length is obtained. With this method a continuous bending process is possible.

Conventional tube-bending machines are already known (e.g., U.S. Pat. No. 2,565,940). The bending operations in such machines are carried out hydraulically and controlled through an actuating carn shaft. The serpentine bends produced through these machines must be corrected and the length deficiencies have to be measured and cut as per requirement (e.g., German Pat. No. 1,080,837).

It is, however, possible to produce serpentine bends with a higher degree of accuracy by using numerically controlled tube bending machines. The movements of the feed carriage, indexing head, as well as bending table are registered through pulse generators. The values for the different movements are fed in the numerical control through punched tape, or punched card, or decade switches.

With the conventional tubebending machines, the operation of matching the stub end of one coil portion to the initial part of a succeeding portion to produce large serpentine coils results in a high tube scrap, which consequently makes the serpentine coils quite expensive.

The invention is embodied in a tube-feeding device, which also works as feed-measuring device. This feeding carriage carries out all feeding as well as measuring operations for determining the stub or leg length remaining in one tube piece, in order to feed from the next tube in the subsequent feeding operation, the amount by which the stub is deficient from the required length. Through this method, it is possible to bend the whole coil for a boiler, for example, in a continuous sequence, and matching operations as well as tube scraps are eliminated.

With the help of the known numerical control, wherein all the values are fed through punched tape, it is possible that the additional program for measuring the leg length deficiency is introduced in the control sequence between bending and indexing operations. This measuring operation is only carried out when a stub leg length occurs.

The place where the end of a stub occurs can be sensed through the invention in difi'erent methods, e.g., the tube end is locatable with the aid of a mechanical feeler, which actuates a limit switch, or a photoelectric cell control, or an induction coil where the value of inductance or induction coil current changes when the tube end is sensed.

It is the general object of this invention to control the tube cold bending operation in such a way that the serpentine bends can be produced out of random tube lengths in a continuous bending process without any matching operation and resultant tube scraps.

Another object of the invention is to provide, in combination with the tube feeding carriage of a tube bending machine, means for sensing the stub end of a tube which has been bent to serpentine form and generating a control signal, representative of the deficiency from a full length between bends, for controlling the initial feed of a succeeding tube to be bent into serpentine form and ultimately joined to the stub end.

Other objects and advantages will appear from the following description and the drawings wherein:

FIG. 1 represents a serpentine coil form ultimately to be produced by bending successive random lengths of straight tubing which are joined into the final coil;

FIG. 2 is a partial top plan view of a tube bending machine embodying the invention, which has bent a piece of tube into a serpentine bent form;

FIG. 3 is the same top view of the tube cold bending machine as FIG. 2, having, however, started to bend the second piece of tube; and

FIG. 4 is a detailed section of a sensor device.

FIG. 1 by way of example, represents the final form of a serpentine coil unit for a steam boiler produced by an automatic tube bending machine from a plurality of random length straight tubes (here two) bent in hairpin bends, the successive equal legs or reaches, S1, S2, S3, S4 of which unit, are each of length L, as measured between the beginning of the semicircular bends. A first tube, tube I (or considered in its bent form a first part 1 of the desired coil), after an initial right angle bend on a first half-length reach, is successively bent in three hairpin bends defining the two reaches or lengths S1 and S2, and then has a residual stub of length RS3 up to its end at V3 (the connecting point to the next part 2) which is deficient from the desired length L to the next bend (or of reach S3) by an amount X. The second separate tube 2, after feeding a start portion (which, of course, must be at last of length A83, i.e., X, plus whatever length of tubing will be consumed in butt or flash welding or otherwise making the joint at V3) is then similarly successively bent at two 180 bends.

With the use of an automatic tube-bending machine adapted to feed the leg length L (S1, S2, S3, S4 etc.) it was hitherto impossible to control the machine in such manner that the first part I of the serpentine coil having the remainder leg or stub length RS3 and the second part 2 with the starting leg length AS3 could be joined at point V3 without any matching work and tube scrap; as it was necessary to determine the length X which in conjunction with L-X (residual or stub length, RS3) would result in the total length S3, and then cut off an excess starting portion of the second coil portion. This hitherto has had to be carried out by a workman manually measuring and then setting up the cutting of the lengths to be joined.

In FIGS. 2 and 3 there is shown the part of a tube-bending machine in which the present invention is incorporated; FIG. 2 showing the first part or coil portion 1 yet clamped in the machine after completion of the last-bending operation, and FIG. 3 showing a succeeding straight tube 2 already fed into the bending mechanism preparatory to a first bending operation in an operational sequence hereinafter described.

The pertinent components of the machine include a divided bend former located at the left end of the machine bed 10 and hydraulically powered to rotate about a vertical axis through a desired angle of tube bending, comprising the die 3 and a cooperating clamping device 4 which is, for example, hydraulically actuated to clamp tube fed thereto for bending (see FIG. 3). Die 3 has a U-shaped external configuration over which extends a groove adapted in depth and shape to embrace about half of the tubing stock circumference, and the clamp jaw in 4 has a similarly sectioned groove opposed to a straight side portion of 3; the semicircular portion of the groove length in die 3 being concentric to the vertical rotational axis.

Further there is provided a tube guiding and stabilizing follower block 5 can'ying a tube clamp 6, hydraulically actuated, for example, again both grooved to cooperatively clamp a tube. In the bending operation accomplished by rotation of die 3 with a tube clamped therein, the follower block is pressed against the bend former die 3 by the hydraulic cylinder 7 as a follower block pressing unit, and also moved by another hydraulic cylinder 8 in the direction of the tube axis to push the tube and also support the straight portion of the tube as it is in effect being relatively wrapped about the curved portion of the die.

The feeding carriage 9, movable on guide ways mounted to the machine base or body 10, includes an indexing device equipped with a tube clamping collet 11, and is driven in its tube feeding strokes H and return strokes by means of a hydraulic motor 16 operating through a rack and pinion ar rangement I7. 3

The collet III clamps the tube in the feeding strokd but opens on the return stroke of the carriage; but also is adapted to clamp the tube in rotating the same by the index device operation as may be required after bending steps or for other purposes; the collet being rotationally driven, by a hydraulic motor of the indexing device, through a desired angle of rotation, for reversing a partially formed coil after each bend (180 reversal for FIG. 1). Where the successive bends are not to be in the same plane (i.e., the coil is not to be flat), the rotation of the collet will then be through a corresponding angle other than 180. To relieve in great part the load on the collet rotational indexing mechanism, a coil reversing or tilting table (not shown) may further be used.

A pinion ll2, rotatably mounted on the carriage 9 and engaged in a rack 13 fixed relative to the machine frame or bed to extend parallel to the path of carriage travel, is connected to a pulse generator I4 whereby pinion rotation produced by travel of the carriage is converted to a series of pulses transmitted, as a signal representative of carriage travel, to a numerical control system for the machine.

The carriage 9 incorporates a tube sensor device disposed adjacent the tube path in the carriage, which device may include any of several known means adapted to sense the presence of a tube and the passage of a tube end, such, for example, as an induction coil the inductance of which abruptly changes when passing a tube end, or a photoelectric cell on one side of the tube responsive to light from a source on the opposite side; or mechanical-electrical means such as that shown in FIG. 4, comprising a spring-urged, tube-contacting finger 10 in camming engagement with a rod 211 operating a switch 22. Thus the device 115, while tubing is adjacent, is in one condition representing a signal or output indicating the presence of tubing; and the change to a second condition upon passing a tube end represents another signal or output indicating the occurrence of the trailing end.

The several functions involved in the running of the machine for producing a serpentine coil such as that of FIG. I are automatically directed by a numerical control system (apparatus not shown) of known type, e.g., programmed by punched tape, to carry out the operations of the various devices in appropriate sequence.

Thus with the carriage at a start position, e.g., the tubing sensing point at the FIG. 2 distance a from the rotation axis of die 3, with parts of the machine (though not the tubing) disposed as in FIG. 3 and a first tube inserted therethrough to establish a standard staring condition, upon operator initiating the programmed automatic sequence, under the numerical control program the clamps 4i and 6 close on the tube, the carriage 9 with collet 11 open returns to the right a programmed distance measured off by the pulses generated by generator 14, which will provide the right-angle top extension in FIG. I, the collet closes, clamps d and 6 open, and a feeding advance of carriage 9 occurs for feeding the measured length requisite for the extension, followed by closing of t and o, collet release, and return of carriage 9 toward the right a distance equal to the length of the unnumbered half-length leg. Then actuation of cylinder 7 presses the follower block 5 toward die 3, as the die 3 (carrying therewith clamp d) begins a 90 clockwise rotation from FIG. 3 position, pulling tubing forward with cylinder 8 simultaneously pushing the tube at the peripheral speed of the die.

The collet I I closes, the clamps 4i and 6 open, also a relative vertical shift occurs between the bend former clamp 4 and the tube thus carrying the latter out of the space between 3 and 4 to provide clearance for reversal of position; cylinders 7 and 8 release or retract; and a feed advance (again to the spacing a in FIG. 2) occurs, feeding the tubing the measured length of the first short leg. Next the indexing mechanism in 9 rotates the collet 180 to reverse the position of the now bend free end, and the bending mechanism returns by a 90 counterclockwise rotation to its starting orientation, clamps 4 and 6 again close, and, with collet ill open, carriage 9 retracts for the length L of the first full leg 5-] again measured off by the pulses generated in M. The actuation of cylinders 7 and 8 follows as before as the bending mechanism 3 begins its clockwise bending rotation this time through 180 at the completion of which the relative orientation of machine parts, (though not of tubing nor carriage 9) of FIG. 2 appears. In such operations, the measuring of a length to be fed, of course, is represented by the extend of the return stroke or retraction of the carriage from its innermost point of advance toward the bending mechanism (at a in FIG. 2), since, after bending, a subsequent feed stroke, with collet closed, to a necessarily advances the tube by the length of the preceeding return stroke.

The same sequence of operations proceeds for the feeding of the length L for the first full leg or reach 8-11 by a first full feed stroke H-l, making the second 180 bend, reversals of the partially formed tube, and feeding the second length for second full leg length S by a second full stroke I-I-2, during all of which the sensor I5 observes tubing available for full length feeding. However, on the return carriage stroke after feeding for 8-5 (after stroke H-2), the sensor observes a trailing tube end, and the signal thereby generated calls up and initiates a special program of operations as follows.

The trailing tube end, indicated in FIG. 1 by the point V3 at which that trailing end is joined to the starting point of a next succeeding formed coil part 2, after bending of the last 180 bend of the first tube or coil part I will become the end of a stub" oi' final partial leg RS3 of coil part 1, which is deficient from the full length L of the reach S3 of the desired final coil by an amount X, that is, the stub length is L-X. Hence there will be required in the coil part 2 about to be formed from the next tube to be bent a starting straight part A83; of length X which is the length complement of RS3, that is, the length X of A83 is such as added to the length (L-X) of RS3 equals the length L of the coil let S-3 (here a common length for all legs). In FIG. 2 the first coil part 1 is shown yet clamped in the machine as it would be immediately after completion of its third 180 bend from which extends the tube stub. However, though the carriage is abo e described as retracting immediately to the point a after each feeding stroke I-Ill, H-2, and before the bending operation, in FIG. 2 the carriage is shown at its innermost, advanced feed position beyond which the tube would be extending further to the right by the length of a semicircular bend before the last bend is made. The total orientational situation of FIG. 2 is that prevailing at the time of completion of a stub-measuring stroke yet to be described.

In the actual return stroke the signal produced by device sensing the tube end V3 brings into operation the sequence to determine the deficiency of the first tube or coil part stub length from the length L of S-3, and to feed the succeeding tube sufficiently for a starting straight part AS-3 which will complement the stub RS-3 by that deficiency to provide length L when the two coil sections are joined. After bending of the third bend, the carriage 9 advances from its fully retracted position in a stub-measuring stroke with collet open.

The advance travel of the carriage, therefore total pulses generated, after the tube end is sensed in this measuring advance stroke then is representative of the length (L-X) of stub RS-3; and the pulse being fed to the numerical control equipment, by the special program now in operation, after taking into consideration the length a from the tube start point on the line through the pivot center of 3 (i.e., the center of the semicircular bend) to the sensing point of 15, causes the controls to perform the operation of subtracting the measured stub length from the desired length L to arrive at the control value for feeding the start of the next tube by an amount to provide the complementing length X in A83 plus whatever known small amount of tubing will e consumed in the subsequent making of the joint at V3 between the two finished coil parts 1 and 2.

At the completion of the measuring stroke, when there is, of course, no need for turning of the now finished first coil part 1, the tube end sensing circuitry is turned off; the cylinders 7 and 3 retract and with the collet 11 open the finished part I is removed; and the bending mechanism returns through 180 counterclockwise rotation, so that the machine can accept a new tube.

The second tube is then inserted as at the start of operations; the operator signals the machine to proceed with the automatic operations, the clamps 4 and 6 close and the carriage backs off for the distance X; the collet closes and with 4 and 6 open the carriage again advances to its inmost operating position completing a feed stroke for the complementary length X. The clamps 4 and 6 close, the collet opens, the sensor circuitry again is turned on and with the collet open the carriage retracts for the length (here again L) of the next leg S4 and the bending operation proceeds for the first 180 bend in coil part 2 followed by feed for S4, bending of the second 180 bend and, where the final coil is to be of the shape of FIG. 1 termination of the automatic program; it being assumed that the second tube length is sufficiently long to yield the rest of the final coil shape, any excess beyond the final short leg length being cut off as required after completion of bending of part 2. However, were a larger coil desired than in FIG. 1, with coil part 2 representing the shape of a completely bent second tube to which a still further coil part is to be joined, obviously the programming may be such as to call up the special stub end measuring program to measure the stub in coil part2 and feed the requisite starting length in the succeeding third tube to provide an initial straight portion before the first bend thereof.

A tube-bending machine embodying the described improvement can proceed automatically through the bending of straight tubes or random lengths to yield coil parts, which may thereafter be joined in the order of successive production by the machine, without special trimming, measurement, or fitting operations. The operation of the bending machine requires operator attention only for unloading, loading, and signalling for resumption of automatic operations; and limitation on the sense of use of the term random lengths" only to the degree that tube lengths used will always result in a measurable and useful stub length for each tube.

We claim:

1. In an automatic tube-bending machine for bending serpentine coil parts from successive straight tubes of random lengths, a plurality of which parts are to be joined in the order of successive bending into a larger coil unit, the lengths of the straight tubes such that the trailing ends will occur on straight stub ends shorter than the straight leg lengths between successive bends of the desired coil unit, said machine including a bending mechanism for bending straight tube fed thereto, that improvement comprising:

means for feeding measured lengths of a tube to said bending mechanism,

means associated with the feeding means for detecting the trailing end ofa tube being fed, and

means responsive to detection of a said trailing end to determine the deficiency of the stub length from the requisite straight leg length and provide a signal to the machine to control the feeding to the bending mechanism of an initial succeeding tube portion of such length as provides, in the coil part bent from said succeeding tube, a complement to the preceeding stub length.

2. The automatic tube-bending machine improvement described in claim l, wherein said feeding device comprises a carriage travelling toward and away from said bending mechanism in advance and return strokes, and

a tube-clamping collet on the carriage closable on a tube thereby to feed a tube length corresponding to a carriage advance stroke portion ensuing immediately after collet clampin 3, The improvement described in claim 2, wherein the said means associated with the feeding means comprises a sensor device disposed on the carriage proximate to the tubing path through the carriage, said device responsive to transit thereby ofa tubing end.

4. The improvement as described in claim 3, wherein said device comprises a switch and tubecontacting means operat ing said switch from one to another switch condition upon passage ofa tube trailing end.

5. The improvement described in claim 3, wherein said device comprises photoelectric cell and light source means.

6. The improvement described in claim 3, wherein said device comprises an inductance coil responding by change in inductance to transit ofa tube-trailing end.

7. The improvement described in claim 3, wherein said machine is numerically controlled through punched tape, and is preprogrammed to carry out the operation of determining the said deficiency only upon detection of a said trailing end.

8. The improvement as described in claim 2, wherein said means responsive to detection of a said trailing end to determine the deficiency of the stub length includes a shaft-driven pulse generator generating pulses proportionately to rotation of its driving shaft,

a first element extending parallel to the direction of travel of said carriage,

a rotational second element secured on the driving shaft of said pulse generator and so engaged with the said first element that said shaft is rotated corresponding to the stroke movement of the carriage.

9. The improvement as described in claim 8, wherein said pulse generator is mounted on said carriage, said first element is a fixed rack, and said second element is a pinion on said driving shaft.

10. The improvement described in claim 9, wherein the said means associated with the feeding means comprises a sensor device disposed on the carriage proximate to the tubing path through the carriage, said device responsive to transit thereby ofa tubing end. 

1. In an automatic tube-bending machine for bending serpentine coil parts from successive straight tubes of random lengths, a plurality of which parts are to be joined in the order of successive bending into a larger coil unit, the lengths of the straight tubes such that the trailing ends will occur on straight stub ends shorter than the straight leg lengths between successive bends of the desired coil unit, said machine including a bending mechanism for bending straight tube fed thereto, that improvement comprising: means for feeding measured lengths of a tube to said bending mechanism, means associated with the feeding means for detecting the trailing end of a tube being fed, and means responsive to detection of a said trailing end to determine the deficiency of the stub length from the requisite straight leg length and provide a signal to the machine to control the feeding to the bending mechanism of an initial succeeding tube portion of such length as provides, in the coil part bent from said succeeding tube, a complement to the preceeding stub length.
 2. The automatic tube-bending machine improvement described in claim 1, wherein said feeding device comprises a carriage travelling toward and away from said bending mechanism in advance and return strokes, and a tube-clamping collet on the carriage closable on a tube thereby to feed a tube length corresponding to a carriage advance stroke portion ensuing immediately after collet clamping.
 3. The improvement described in claim 2, wherein the said means associated with the feeding means comprises a sensor device disposed on the carriage proximate to the tubing path through the carriage, said device responsive to transit thereby of a tubing end.
 4. The improvement as described in claim 3, wherein said device comprises a switch and tube-contacting means operating said switch from one to another switch condition upon passage of a tube trailing end.
 5. The improvement described in claim 3, wherein said device comprises photoelectric cell and light source means.
 6. The improvement described in claim 3, wherein said device comprises an inductance coil responding by change in inductance to transit of a tube-trailing end.
 7. The improvement described in claim 3, wherein said machine is numerically controlled through punched tape, and is preprogrammed to carry out the operation of determining the said deficiency only upon detection of a said trailing end.
 8. The improvement as described in claim 2, wherein said means responsive to detection of a said trailing end to determine the deficiency of the stub length includes a shaft-driven pulse generator generating pulses proportionately to rotation of its driving shaft, a first element extending parallel to the direction of travel of said carriage, a rotatioNal second element secured on the driving shaft of said pulse generator and so engaged with the said first element that said shaft is rotated corresponding to the stroke movement of the carriage.
 9. The improvement as described in claim 8, wherein said pulse generator is mounted on said carriage, said first element is a fixed rack, and said second element is a pinion on said driving shaft.
 10. The improvement described in claim 9, wherein the said means associated with the feeding means comprises a sensor device disposed on the carriage proximate to the tubing path through the carriage, said device responsive to transit thereby of a tubing end. 